Timing Calibration of the NuSTAR X-ray Telescope

Matteo Bachetti , Craig B. Markwardt , Brian W. Grefenstette , Eric V. Gotthelf , Lucien Kuiper , Didier Barret (1) , W. Rick Cook , Andrew Davis , Felix Furst , Karl Forster , Fiona A. Harrison , Kristin K. Madsen , Hiromasa Miyasaka , Bryce Roberts , John A. Tomsick , Dominic J. Walton

1 IRAP - Institut de recherche en astrophysique et planétologie

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission is the first focusing X-ray telescope in the hard X-ray (3–79 keV) band. Among the phenomena that can be studied in this energy band, some require high time resolution and stability: rotation-powered and accreting millisecond pulsars, fast variability from black holes and neutron stars, X-ray bursts, and more. Moreover, a good alignment of the timestamps of X-ray photons to UTC is key for multi-instrument studies of fast astrophysical processes. In this paper, we describe the timing calibration of the NuSTAR mission. In particular, we present a method to correct the temperature-dependent frequency response of the on-board temperature-compensated crystal oscillator. Together with measurements of the spacecraft clock offsets obtained during downlinks passes, this allows a precise characterization of the behavior of the oscillator. The calibrated NuSTAR event timestamps for a typical observation are shown to be accurate to a precision of ∼65 μs.

Domaines: Instrumentations et Détecteurs [physics.ins-det]; Astrophysique [astro-ph]

Matteo Bachetti, Craig B. Markwardt, Brian W. Grefenstette, Eric V. Gotthelf, Lucien Kuiper, et al.. Timing Calibration of the NuSTAR X-ray Telescope. Astrophys.J., 2021, 908 (2), pp.184. ⟨10.3847/1538-4357/abd1d6⟩. ⟨hal-02966408⟩